Tool-grinding machine



F. L. WACHTLER. TOOL GRINDING MACHINE.

APPLICATION FILED ocT; 16, 1919 1,429,808., Patentedsepm9,1922.

TSHEETS-SH E E F I.

F. L. WACHTLER.

TOOL GRINDING MACHINE.

APPLICATION FILED OCT-16, 1919.

1,429,308. v at n easept. 19, 922,

7 SHEETS-SHEET 2.

F. L. WACHTLER.

TOOL GRINDING MACHINE.

APPLICATION FHLED OCT. 16, 1919.

1,429,308, PatentedSept. 19, 1922.

7SHEETSSHEET 3.

F. L. WACHTLER.

TOOL GRINDING MACHINE.

APPLICATION FILED OCT. 16, 1919- 1,429,30 Pa tented Sept. 19, 1922;

7 SHEETS-SHEET 4.

F. L. wAcHTLg-iR TOOL GRINDING MACHINE.

APPLICATION FILE D OCT. 16. I919- Patented Sept- 19,1922.

7SHEETS-SHEET 5- I F. L. wAcHuE TOOL GRiNDlN-G MAQHINE.

APPLICATION FILED OCT. 16, 1919.

' l u ".127 sS HEETS-SHEET a.

l ,2 A f Y Ha:

Patented Sept. 19, 1922.

Patented Sept. 19, 1922. I

FRANZ LoUIs. WAGHTLER, -or anossnmram, GERMANY.

; TOOL-GRINDINGMACHINE- Application filed October 16, 1919. Serial No.331,212,

To all whom it may concern: I Be it known -that I, FRAN LOUIS Wiiorrr-LER, a citizen of the Republic of Saxony, Germany, residing at'Grossenhain, Germany, have invented certain new and useful Improvementsin Tool-Grinding Machines (for which I have filed applications inGermany, G. 46,302 XII/67 dated 21st of Feb-- ruary, 1918; Germany, G.46,536 XII/67 dated 13th of April, 1918; Germany, G,

are disposed on a reciprocating slide, so that Y the tool is passedbefore a stationarily journaled revolving grindingpdisc, still show+even if working automaticallymany drawbacks, whichresult in the teeth tobe ground being attacked veryunevenly by the grinding disc; SQ that'theheight'of the ground teeth variesand'the latter do not attack the workevenly; the consequence is that the projecting teeth easily break off,and

the toolatoleast is'soon blunted and becomes useless. Under aninaccurately regulated pressure the cutting'edges of the tools arefrequently also heated so that they become soft and unserviceablebecause the'reciprocated tool can be ground only while the tooth ispassing the grinding-wheel in one direction, as the dead point in thefeed gear renders it impossible to press the toolagainst the grindingwheel while the tooth is passing the latter in the opposite direction.'Therefore automatic tool grinding machine work uneconomically,.even ifthe return of the tool isaccelerate'd.

All these drawbacks are obviated by the new tool grinding machineaccording to the present invention; besides further advan-.

tages are-derived, which shall hereinafter be disclosed by thedescription of the construction'jof the'machine itself.

A feature of the machineaccording to the I present invention consiststhereinthat the spindle of the center pointsupporting the one endof themandril is *iournaled so as to revolve freely, whllst it is held in acertain position (grindingv position) by-means action frictionally' onit, whichmeans are adapted to cause, by a corresponding control, arevolution of said spindle in the one direction; the said means,furthermore, will admit of a revolution of the spindle in the oppositedirection when a force, greater than the grinding pressure acts on thespindle, so that the mandril will on the one hand be held during itsreciprocation in its grinding position by means frictionally acting onthe center pointspindle, and may, furthermore, be turned by the sameduring the operation when tools with helical teeth are being ground,whilst on the other hand the turning of the tool with reference to thepitch of its teeth may be performed "durv ing the grinding operation andwithoutsaid frictional means being disengaged, as soon as-the tool hasmoved out ofithe range of the grinding wheel. v

It is further necessary that the gear parts which produce said turningof the tool engage only at the very moment necessary for the reversing,and are immediately after again disengaged, so as to allow the mandrilto revolve freely, independent of all, gear parts employed forsaidturning. As everywhere in mechanical"construction the'most simpledesign will also here lead to securing a perfect working of the turninggear; therefore the known.,device of a ratchet wheel and pawls hasbeen-employed, said ratchet wheel having a number'of notches for theengagement of 'the pawls, said notchescorresponding in number with thenumber of teeth on the tool' to be ground, so'that by simply exchangingthe ratchet wheel the turning or dividing gear as we may call it,

may be readily adapted for tools of-any number of teeth, Theintentionito secure the 'most simple design has furthermore lead tosecuring the said ratchet wheel immediately "on the mandril. Thisnecessitated that the engagement of the pawl with the ratchet wheelcease immediately after the desired turn has taken. place. According tothe present invention this is obtained by the pawl being carried by aspur wheel freely revoluble on the mandril. This spur wheel meshes witha Wheel on a haft pap frictionally journalled in the mandril headstock.1 When revolved in one sense the said extension abuts against the oneside of said recess, and thereby the pawl is brought into engagementwith the ratchet wheel. When; revolved in the opposite sense the saidpawl extension will abut against the other side ofthe recess and therebythe pawl is lifted fromf the ratchet wheel. By such. simple means itispossible to holdthe pawl in engagement with the ratchet wheel fitted d1-rectlyvon the mandril duringthe' time only,- which it is necessary forthe respective turning, whilst during the other time,that is during theoperative stroke, the mandril can revolve fully freely. -By the ratchetwheel being fitted directly on the mandril, all troubles by intermediategears are obviated, which, as experience has proved,cause an inaccurateadjusting or setting of the tool.

Oncethus provision has been made that the setting of the tool relativelyto the grinding disc'may. be performed independently of the dividinggear, also provision must be made for a proper operation of the machine,and also that the grinding wheel itself is reliably-held in its positionduring the whole operation. In grinding machines, however, in which the.shaft carrying the grinding tool or wheel runs at a high speed, it has ibeen found that the said shaft readily heats considerably in itsbearings. This leads to an elongation of the shaft, which 'willthereafter axiallyvibrate. This again will have the result that theposition'of the grinding wheel varies, so that the tool is submitted toan inaccurate grinding, more being ground of at some parts, less atothers. This evil cannot be obviated by readjusting the heated shaft,because such readjusted shaft would seize on cooling down subsequently.

It is the object of the present invention to obviate also such drawbacksby arranging the shaft in such a manner that it is possible tocompensate the change in the ,lengthof the shaft carrying the grindingwheel in such a manner that the said grinding wheel will always remaininexactly'the same place and the shaft does not vibrate axially in itsbearings.

In the accompanying drawingsFigures 1 and 2 show the grinding machine inelevation, Fig. lbeing a side elevation and Fig. 2 an end elevation,seen-in the direction of the arrow in Fig. 1. Fig. 3 is a verticallongitudinal section through the 'mandril with the respective drivinggear. Fig. 4 is an end elevationseen in the direction of the arrow inFig. 3. Fig. 5 is an approximately mandril 12 carrying the tool 11.

horizontal section on the line 55 in Fig. 4.

tions thereof, in the one the chain wound around the spindle or itssleeve, respectively, having been omitted; Fig. 9 is an elevation of themandril head stock seen from the rear; Fig. 10 is a detail sideelevation partly in section of the mandril head stock; Figs. 11 and 12show the dog and the grinding wheel. Figs. 1317 refer to a modifiedconstruction of the brake device; Fig. 18 being again an elevation ofthe mandril headstock, Fig. 14: a vertical central section therethrough,and Figp15 an elevation of the mandril headstock seen from the rear;Fig. 16 is a special modification of the means of securing the chain;Fig. 17 is a top view of the chain stretched out. Fig. 18 is alongitudinal section showing the journalling shaft in two differentpositions, both seen from above.

From the driving shaft 1 (Figs. 1 and 2) the shaft 2, axially shiftablein its lower bearing, is driven by--means of worm and worm wheel; theupper end of this shaft 2 is journalled in an overhang bearing of thebody part 4, which may be raised and lowered by means of handwheel 5 andscrew spindle 6. At the upper end of the vertical shaft is disposed acr'ankwith connecting rod 7, which acts on a slide 9 guided on the slidetable .8yand reciprocates the said slide. On said slide is fitted theheadstock 10 and the mandril headstock 12. Between the center'point ofthe mandril headstock and the center point of the headstock 10 is fittedthe By such means the tool is carried past the revolving grinding wheel13, the shaft of which is supported in the forked bearing 14:, when theslide 9 is reciprocated.

Close to the upper end of the vertical shaft 2 is fitted a cam-disc, onthe surface of which is disposed aroller 15, carried by lever 16 ,keyedto a horizontal shaft 17. In consequence thereof this horizontal shaftwill be oscillated by the lever 16 as the roller overrides theprojection on the cam disk at each revolution of the vertical shaft 2viz, each time after the reciprocation of slide 9 on table 8 has beencompleted. This oscillation of shaft 17 is transmitted by rod gear to ahorizontal shaft 19 disposed parallel to the mandril spindle 18 (seealso Fig. 5). From 'shaft.19 the oscillation is transmitted, by

described by what means hereby the oscillation will during suchtransmission act in one sense only on the said man-dril splndle. By suchmeans after each operative stroke, 1. e.,

after each complete reciprocation of the-tool,

rec

the latter is advanced by one tooth, so that.

' a fresh tooth will come into contact with the grinding wheel.

' Themandril spindle 18 (Figs. 3 and 5) which isrigidly secured theretoby means of a nut'24 and a washer 25. The spindle runs in two ballbearings, disposed in theparts' 26 and 27 of the forked headstock 12.The

ball races 28-on the spindle 18 are held by means of an intermediatesleeve 29 and nuts 30'and '31. The ball races 32 in the; bearings 26 and27 are secured by means of a 'nut 33. On-an extension of theboss ofpart'26 is fitted freely revoluble a spur gear 21, on which -a ring 34is screwed. This ring 34 has. a pin 35 on which is fitted a' pawl 36,which-cooperates .with the'ratchet wheel 23 in a mannerto be hereinafterdescribed. 0n the inner side of'the extensiorf-of boss 26 an annularbody is'frictionally coupled thereto by means of a slip spring 37, saidannular .body having an upwardly extending horn 38 (Fig. 4). This hornhas at its upper end a recess 39, in which engages a nose on the boss ofpawl 36.

The gear 21 carrying the pawl meshes, as beforesaid, with the gear '20-onshaft 19. This shaft '19, which is parallel to the manedril spindle isoscillated in the. following manner: From the vertical shaft 2 thehorizontal shaft 17 ,to which lever 16 is fitted, is oscillated once ateach' operative stroke by -means ofithe cam disc and the lever 16engaging with roller 15 in the groove of said cam disc. To the one endof shaft 16 is fitted a lever 41,'having in its free end a curved guideslot. In this guide slot a block fitted to the end of a rod 42 may beadjusted. The said rod 42 acts on a lever 43 which is fitted freelyrevoluble on shaft 19 (Fig. 5). On"

gear train has been employed in order to. allow ofreadjusting the toolrelatively to' the grinding wheel. Such readjustment may be necessary inconsequence of the wear of the grinding wheel and the tool in course oftime. For this purpose the pin 46, carrying the gears 45 and 47, isfitted to a worm wheel 49, the worm 50 of which may be turned by meansof a hand wheel 51. The turning of the worm wheel will cause the gears45 and 47 to roll on the respective gears 44 and 48 and to thuscause alead or lagging of the shaft 19, which means a fine adjustment of thetotal relatively to the.

grinding wheel. The gear 20 fitted to shaft performed in the followingmanner:

19 is axially adjustable withits bearing car'- ried by slide 9, forwhich purpose a key 52 to of suitable length has been employe hold gear20 to shaft19.

The mandril 12 with the tool 11 is held inoperative position in thefollowing manner: On the sleeve 29 fitted to the mandril spindle 18 iswound a chain (Fig. 8).:. The one. end'of this chain is run over aroller 53 and carries a weight 54. The

otherend of the chain is coupled toa slide 55. This slide'tr'avels' inguides 56 crosswise to the axis of the mandril spindle, the said guidesbeing fitted to the headstock 111. 111 v the middle of the guides 56 isdisposed a pin 57, on which a pawl 58 is pivoted. This awl can be thrownover so that it engages in a recess '59 in slide 55 (see dotted lines inFig. 8). When the said pawl thus engages in the recess in slide 55, thelatter will be held in'a givehyposition, the pull of the weight 54 on.the chain forcing the slide against the pawl. weight; the chain woundaround sleeve 29 has a high friction on the latter, the mandril spindle,which is freely revoluble in its hearings 26 and 27 is held in itsposition determlned by the position of the slide. The friction of thechain is so great, that it exceedsthe grinding pressure. It is onlynecessary to provide that this position of the sleeve 29, andthereforealso on the mandrilfspindle 18 corresponds to the operativeposition, i. e., that position in which the tool bears with the faceof-one of its teeth against the grinding wheel 13. The fine adjustmentis Asr now, owing to the performed by aid of handwheel 51 in the mannerhereinbefore described.

When, now, a fresh tooth .of the tool is to be' brought into contactwith the grinding wheel, the tool will have to be advanced, and thiswill have to be at the moment when'the tool has been moved out of therange of the grinding wheel, i. e., after it, during its reciprocatingstroke, has been passed twice along the grinding wheel. This advance isThe gear 21 carrying the pawl 36 meshes in the manner hereinbeforedescribed with gear 20 on shaft 19. Shaft l9.is oscillated, thereforealso gear 21, carrying pin 35 of the pawl. Therefore also the extension40 is. oscillated. If now the oscillation proceeds in the direction ofthe arrow in Fig. 4, the extension will bear against the left side ofthe recess 39. Thereby the pawl 36 is pressed into the ratchet wheel 23.notch therein and thus produces the movement necessary forturning themandril recess 39 and thereby the pawl is lifted out from theratchetwheel. At a further turn in this direction the shoulder 60 of extensionIt engages in .the next.

40 finally bears against the'upper end of the part 38 having therece'ss'39, so that said part 38 is. dogged against the action of its tothe twist of the teeth of the tool.

cal'twist of theteeth. This twist may be" performed by ,the .partsproducingthe ad- Vance without aifecting the mandril spindle,because'the pawl is lifted out immediately after the advance hasbeen-completed. The arrangement which produces the twist of the mandrilspindle in correspondence with the .helic'altwist of the tool must be soconstruct- .ed that it allows of the spindle being twisted during theadvance. 4 The mandril spindle is twisted in correspondence'with thehelical twist of the tool teeth is performed by aid of the hereinbeforedescribed slide 55. This slide-has at its lower end a roller 61, with.

which it engages; on a guide-bar 62,- when the pawl 58 is lifted. Thisguide bar swivels on a central pin 63 and may be fixed in any adjustedposition. The guide bar is stationary' and therefore does notparticipate in the reciprocating movement of slide 9 on table 8. On theother hand the slide 55 gliding crosswise to the axis ofthemandrilspindle is dogged together with its guides 56 during the reciprocatingmovement of the tool. In follows therefrom that the slide will duringsuch reciprocating be lifted and. lowered by the slantingly disposedguide bar 62. The adjustment of the guide bar must correspond slide 55is held with its roller 61 down on the guide bar 62 by means of theweighted chain. The pull of this weight has the effect thatthechain'wound on-thesleeve 29 exerts a pull on the slide 55, on the onehand, and

' on the other that on the slide 55 being raised and lowered, 'by thefriction of the said chain'the sleeve 29, and with it the mandrilspindle 18 is dogged.

According to the present. invention the chain is constructed in suchamanner that its upper part. acting on the slide 55 is composed of twoparallel thrums 64, whilst the lower, weighted part consists of onethrum 65 ,only,,in such a mannerthat the part 65 remains in the gapbetween the two thrum's 64, where the chain is wound. on the sleeve 29.;Thereby it is possible that the middle I line of the chain alwaysremains in the same plane'althou h the chain is wound on the sleeve 29.hen now a force appears which tends to turn the sleeve in the direct-ionof the pull of we1ght'54, viz., contrary to the arrow shown in Fig. 8within the sleeve 29,

thefricti'on ofthe chain on sleeve 29 will oppose such force. Such forceis the grinding 65 pressure exerted by the grinding wheel on The- eaeoathe tool. When, on the other hand, a force appearsywhich tends to turnthe sleeve 29 and the man'drilvspindle 18 in. opposite direction--viz.,in the direction of the arrow shown in Fig. 8 inside of the sleeve29-such turning may proceed without any'difiiculty, as the weight actstowards slackening the 'ehain. Such turning will proceed when theadvance is being" made, as in this case the mandril spindle 18 is by theratchet gear '23, 36 dogged in the direction of the arrow (Figs. 4 and8). The advance will therefore notaifect the weightin parts, whichproduceflthe twisting of the mandril spindle 18 taining this roughadjustment the dog,

which couples the mandril with the mandril spindle, is-made of a specialform. This dog consists of a part 66'screwed to the end of the mandril.On a screw bolt 67 (see Fig. 11) are fitted two jaws 68, one to theright and one to the-leftof the part 66 screwed to the mandril. Thesejaws form a fork. They engage in a circular groove 69 in the nut 31onspindle 18 and are of a corresponding curvature. When, now, one of thenuts 70.0n the endof bolt 67 is tightened, the jaws68 are clamped bothto the dog 66 and into'the annular groove 69. By such means the mandril12 is dogged. As soon as one of the nuts is loosened, the clampingpressure ceases which holds the jaws 68 in the annular groove 69. Thenthe dog Ina be turned at will with the mandril l2. This'possibility ofturning the mandril is employed for rough adjusting the tool. If one ofthe nuts 70 is loosened, and the center point is withdrawn into theheadstock 10 by turning handwheel 71., the mandril 12 may be taken withthe tool from'the machine. I

In Fig. 12 the grinding wheel 13 is shown in contact with the tool 11.One may see hew the tooth being ground bears with its face against thegrinding surface. The ar-' row indicates the direction opposite to thatin which the mandril must be. advanced for the nexttooth to be broughtinto contact.

accurate adjustment, which exactly corre- .sponds to the pitch. of therespective teeth of the tool. F or this purpose an arrangement isprovided,-which may be termed the micrometer adjusting attachment. 9

The guide bar 62 islcoupled by means oi .inbeforedescribfed will not ornot very well a bolt 71 (Fig. 10) with asector72 pivoted on a pin. 63'This sector forms a part of a worm wheel and meshes with a worm 73.

The worm, to which 'a handwheel 74 is at tached, is fitted freelyrevoluble on the one.

leg ofan angle bolt '75 .(shown separately below Fig. 6). Theother endof the angle bolt engages in an arm 77 extending from the bearing 76 ofbar 62. On a collar 78 on-bol't 7 5 is a mark (a cut) and on the collar79 of the .worm is a graduation from 0 9, To the end of'bolt 75 isattached a pointer 80, the point of which plays over a dial on sector 72: The zero of this dial coincides with the point of said pointer, whenthe guide barv 62 is absolutely horizontal,

thus in an indiflerentposition, and therewillbe' no twist of themandril. The dial is so divided that at each full revolution of the wormthe sector will be moved by one graduation relatively to the pointer.The graduation-on the collar of the worm allows the operator/to set theattachment to 1/10 of a divisionof the dial on the sector. The guide bar62 can be fixed in-any adjusted position by means of nut 81 on bolt 63..

The mark on bolt 75 may also be omitted and the reading may be madealong. the

pointer.

I The tool bears in the manner shown in Fig. 12 with the face of one ofits'teeth against the grinding wheel l3.

According to the present invention a chain weighted or under action of aspring is wound around the mandril spindle which is journalled freelyrevoluble in its bearings; the upper end of'said spring being at-'tached to a slide which may travel crosswise to the axis of saidspindle'and be fixed. I

The pull of the weight or spring has the effeet that the spindle is heldby friction with the chain in its operative (or grinding) position,providing that the grinding pressure. of the spindle acts in thedirection of the pull of'the weight or spring. If, however,

the spindle is turned opp'ositelyto the pull of said weight orspring,this may be per-.

formed without any nominallresistance, so that such turning'may beutilizedfor the advance of the toolorthe accurate ad ustthe end of thechain is .attached,-is moved,

' main.

the spindle will be turned,'the hereinbefore described :c onditionsregarding the resistance against't-he turning of the spindle in by meansofthe slide is utilized, when tools siderable pressure, thearrangementshereperience that the chain'be wound several in such amanner that the links are set off mentof. the same. When the slide, towhich The rotation of the spindle producedwith helical teeth are to beground, with When toolshave to beground ata contofore disclosed, andincluding" those here- 7 hereinbefore described arrangement by inacreasing the pull ofthe weight ,or the spring. By thus increasing thebrake effect, however, also the advance of the tool will become moredifiicult, so that it is either necessary tomake provisions, to annulthe brake effect during the. advance, or to heavily weighten theadvancing'gear, for it to overcome the frictional resistance.- In eitherinstance. the grindingwill suffer thereby, by springeffects beingintroduced into the gearing, which will impair the production ofstraight ground surfaces. f

Whereas in the'hereinbefore described arrangement the chain is .woundonce only .around the spindle, the present invention provides for suchpurpose according to extimes around the spindle. -It is thereby securedthat the spindle cannot by any means he turned in the direction of thepull of the chain, because the'frictional resistance is tooextraordinarily great, that it will resist even the highest grindingpressure; ..but the spindle may without any essential resistance beturned inthe opposite direction the same as before. It is therebyobtained that on the one hand the brake effect on the spindle will meetvery high grinding pressures,

whilst on the. other hand, the; possibility of readily turning thespindle for advancing the tool is not reduced.

It is, insuch case, important, that'the individual turns'of the chain donot touch each other, because, as soon as the spindle is v turned fromthe slide, to which the. end of the chain is secured, the chain will nomore be stationary but be partially wound or unwound, respectively,whereby the thrums, if 4 they rub against each other, would not onlyi'inpare' the effect but also be destroyed by wear. For preventing thisthe 'part of the chain which is to wind on the spindle is made 2 meas esglides between the guides 81 connected by set-screws, which may be setat will from the handwheel 74 by means of a worm gear, so

that when theheadstock 111 is shifted longi tudinally,-the slide 55 ismoved transversely,

when the guides 81 are set at an angle (con trary to the position shownin .F i 13).

To the upper end of the slide 55 is attached the chain 64. This chain iswound in several (3) turns around the spindle or a sleeve 29 connectedto the spindle, said sleeve being freely revoluble in the bearings 26,27 of the headstock. The other end of the chain is attached to a springbolt 82, which is fitted axially displaceable to the lower end of theslide 83 and is pulled downward. by 'th spring 8 1 around it.

The spring 84 need be only quite weak, be-

cause the three turns of the chain on the spindle will already afford sogreat a frictional resistance against the turning of-the spindle in theone direction, that no con.- siderable pull by weight or spring on .the

. end of the chain is anymore required. The

object is only to yieldingly secure the end of the chain, so as to keepthe chain in order in its position.

As may be seen in particular from Fig. 17, the chain is so constructed,that its two ends .64 and 64 extend in a straight-direction.

The part of the chain, however, which winds on the sleeve 29 has itslinks set off to one side, so that the individual turns of the chain onthe sleeve 29 willnot touch each other (Fig. 15). When the spindleisthere- 'fore turned, by the travel of the slide 55,- the chain,winding onto or unwinding from the spindle, cannot rub with its turnsagainst each other.

3 In the form shown in Fig. 16 the slide 55 is provided with a rack inwhich engages a gear 86 loosely revoluble on'sleevc 29. To-

grinding wheel 13 to be secured by means of the screw thread 87.

The invention wliich. is intended to be chiefly employed with precisionmachine tools with high-speed spindle in thrust bearings, provides thatthe'shaft revolves with.

two conical collars tapering towards each other, 88, 89 in twocorrespondingly bored journals 90, 91. This type of bearing is employedforreason'of the greater possibility of accurately adjusting the same.

Ifnow, as it is the case in the left hand bearing with regard to cones92, 93 and with the right hand bearing with regard to the cones 88, 89the two cones of the bearing are .fixed relatively to'the shaft .(on theleft sleeve 941) an axial play will appear in the bearing on the latterbeing much heated, so that the spindle will greatly vibrate and theaccuracy of the work will suffer. In the bearing shown-this trouble willbe particularly noticed in the right hand bearing, be

cause the-latter is under the greater load, the

bearmg.

I may here point out that even 1f an even heating of the two cones 88,89, on the one one hand, and of the sleeve'90 on the other be supposed,the sleeve must expand radially more when the sleeve is madein the usualand approved manner of gun metal, because the cones are made of steel oriron, when thus the metal of the sleeve has a higher coeificientof-expansion. The greater expansion causes the fit to slacken the more,

because it produces a radial'receding of the conical. line of the sleeve90 from the angle formed by the cones, thus a relative shortening of thesleeve, which cannot be compensated by the greater longitudinalextension of the sleeve as a consequence ofthe higher coefficient ofexpansion.

-F or the purpose of maintaining the original fit even when the bearingsheat,

thetwo cones 88, 89 will,thereforehave to be approached towards eachother in approximate correspondence withthe increasing heat or theexpansion,respectively. According to the present invention the heatproduced by the slipping of the belt is utilized in such a manner, thatone of the cones, viz. 88, is formed by a sleeve 99 made in the form ofa belt pulley 98. By said sleeve 99, which drives the spindle 96 bymeans of a key 100, bearing against the abutment formed by the locknutslOl, 102,

it will, on being heated by the slip of the belt, force. the cone 89 totheright towards the cone 88 rigidly fitted to the spindle 96. As a heatproducing agent not only the slip of the belt (which just at high speedsand small pulleys is unavoidably great.) but also the lateral shiftingof the belt (which likewiseappearsunder the said conditions with a highnumber of oscillations). Besides the same as the heating of the bearing,also the heating of the sleeve 99 by the slip of the belt will increasewith the duration of the work and with the load, so that the utilizationof the slip of the belt as source of Heat for producing the expansion ofa slackening of thefit of the bearing caused by the heating of thelatter.

The locknuts 101, 102 allow, as anad-' justable abutment the regulationof the fit of the bearing.

. For adapting-the grinding wheel to the twists of tools with helicalteeth, the'bearing 14 of the grinding wheel shaft is, as

groove is curved to 'a circular line 107 the center of which is situatedat w (see also arrow in FigI-QO), viz., inthe vertical middle line ofthe grinding 'wheel 13. By shifting the sliding bearing the grindingwheel 13 may be brought into any angular position, one of which is shownin Fig. 20.

The intermediary position of the grinding wheel 13 shown in Fig. 19 isemployed for tools with straight teeth.

With the new girinding machine both, tools-with pointed and withundercut teeth may beground, it being immaterial whether their teeth areparallel to the axis of the tool or helically wound to the right or theleft, grinding wheels of any kind being used. I claim: 1. In a toolgrinding machine in which i the tool .is fitted on a mandril heldbetween two center points fitted to a reciprocating bination of a freelyrevolubly journalled spindle carrying the one of said center points, aflexible element wound around said spindle, a tensioning elementconnected to one end of said flexible element,theother end of saidflexible element attached toa controlling member shiftable crosswise tothe axis of the said spindle; k

2. In a tool grinding machine in which the tool is fitted on a mandrilheld between two center points fitted to a reciprocating slide, whichmovesthe tool past a stationarily revolving grinding wheel, thecombination of a freely revolubly journalled spindle carrying the one ofsaid'center points, a flexible element wound'around said spindle, atensioning device connected to one end of the flexible element, theother end of said flexible element attached to a slide shiftablecrosswise to the axis of the spindle, apawl engaging in and arresting.rides on said adjustable guide rail,

said slide, an adjustable guide rail, anda roller on said slide, withwhich said slide when not arrested by said pawl.

3. In a tool grinding machine in which the tool is fitted on a mandrilheld between the two center points fitted to. a reciprocating slide,which moves" the tool past a stationarilyjrevolving grinding wheel, thecombination of a freely revolubly journalled spindle carrying the one ofsaid center points, a flexible element loosely Wound around saidspindle, a tensioning device connected to one end of said flexibleelement,

the other end of flexible element attached to a slide shiftablecrosswise to the axis of the spindle, a pawl engaging in and arrestingsaid slide, a guide rail adjustable on a pin and a roller on said slide,with which said slide rides on said adjustable swivelling rail, when notarrested by said pawl, said chain holding said slide down against saidguide rail, said guide rail fitted with a 'wormwheel sector, engagingwith a worm rily revolving grinding wheel, the combination of a freelyrevolubly journalled spindle carrying the one of said center points, a

flexible element consisting by one half of two parallel thrums, in theother half of one central thrum adapted to'engage in the gap between theother two thrums, said chain wound with its two-thrum part looselyaround said spindle, the one-thrum end of said chain carrying a flexibleelement, the other two-thrum end attached to a slide shiftable crosswiseto the axis of the spindle a pawl engaging in and arresting said slide,a guide rail swivellingly adjustable on a pin and a roller on saidslide, with which said slide rides on saidadjustable swivelling guiderail, when not arrested by said pawl,

said chain holding said slide down against said guide rail, said guiderail fitted with a worm-wheel sector, engaging with a worm havingahandwheel, andapointer and dial for reading the relative adjustment ofsaid worm and sector. Y

5. In a tool grinding machine in which the tool is fitted on a mandrelheld between two center points fitted to a reciprocating slide, whichmoves the tool past a stationarily revolving grinding wheel, thecon'lfbination of a freely revolubly journalled spindle carrying the oneof said centerpoints, a

flexible element, wound around the said spindle, the one end of saidelementcarrying a tensioning device, the other end of said elementattached to a controlling member shiftable crosswise to the axis of thesaid spindle,

a ratchet wheel having the same number of teeth as the .tool to beground fitted on the spindle holding the mandrel, a pawl engaging insaid ratchet wheel and carried by a member, revoluble on the mandrelspindle, means for oscillating said member on the 1 tool is fitted on amandril held between two:

eaaeoe completion. of the reciprocating operative 9. In a tool grindingmachine in which 65 stroke of the mandril, on said pawl an extension, acontrolling member held by fric tion in the mandril spindle bearing andhaving arecess, in which said pawl extension engages.

6. In' a tool grinding machine in which the center-points fitted to areciprocating slide, which moves'the tool past a stationarily revolvinggrinding wheel, the combination of a freely revolubly journalled spindlecarrying the one of saidcenterpoints, means ac-ting on said spindle andadapted to turn said spindle in one direction, to hold said spindle in agiven position (grinding position) and to allow of the said spindlebeingturned 1n the'opp'osite direction on a force exceeding the spin le, aslide carrying the grinding wheel, said slide having a web or the like,in the slide table a groove of a circular curve, the center of saidcircular curve beingin the vertical middle line of the grinding wheel,said web engaging in said groove.

.7. In a tool grinding machine in which the tool is fitted on a mandrilheld between two center points fitted to a reciprocating slide,-

which moves the tool past a stationarily revolving grinding wheel thecombination of a freely revolubly journalled spindle carrying the one ofsaid center points, means acting onsaid spindle, adapted to. turn saidspindle in one direction, to'hold the said spindle in a given position(grin'dingposition) and. to allow of the said spindle being turned inthe opposite direction on a force exceeding. the grinding pressureacting on the said spindle, the grinding wheel spindle having a doubleconical bearing, the one of the cones formed by asleeve non-revolublyfitted to. the spindle, and bearing against an abutment on said spindle,said sleeve so formed as to simulta neously serve as belt pulley. f

8. In a tool grindingmachine in which the.

the said spindle, the grinding wheel spindle having a double-conicalbearing, the one of the cones formed by a sleeve non-revolubly fitted tothe spindle, and bearing against an abutment on said spindle, consistingof two rindin'g pressure acting on the said the tool is fitted on amandril held between two center points fitte'd to a reciprocating slide,which moves the tool past a station-- arily revolving grinding wheel,the combination of a freely 'revolubly journalled spindle carrying the"one of said center points, a chain wound several turns, around saidspindle, in-the part of the said chain -which is thus wound around saidspindle the links continuously set off on one side, the one end of saidchain carrying a tensioning device, the .other end of said chainattached .to a cont'rollin crosswise to the axis o the said spindle.

10. In a tool grinding machine in {which the tool is fitted on a mandrelheld between two center points fitted to a reciprocating slide, whichmoves the'tool past a stationarily revolving grinding wheel, thecombination of a freely revolubly journalledspinmember shiftable dlecarrying the one of said center points,

a chain wound several turns around said spindle, in the part of the.said chain which is thus wound around said spindle the linkscontinuously set off on one side, theone end of said chain.carrying a.tensioning device, the other end of said chain attached to a slideshiftable crosswise to the axis of the spindle, a block on said slide,two guides adapted to be obliquely adjusted, said block on said slide,sliding between said adjustable guides.

11. Ina tool grinding machine, a cutter shaft adapted to carry a cutter,a tool supporting spindle adapted to carry a tool, means forintermittently advancing said spindle in strokes of predeterminedlength, .and adjusting means for causing the lead and lag ofsaidstrokesdependent upon the relative wear and adjustment of said cutter and toolfor maintaining desired pressure between the same.

12. In a tool grinding machine,"a cutter shaft adapted to carry acutter, a tool supporting spindle adapted to carry a tool, areciprocating -member for advancing said spindle instrokes ofpredetermined length, and variable adjusting means arranged between thereciprocating member and the spindle for causing the lead and lag ofsaid tool and cutter.

13. In a tool grinding machine, a cutter shaft adapted to carry acutter, a tool supporting spindle adapted to carry a tool, areciprocating member for advancing the spindle'in strokes ofpredetermined length, a differential mechanism connected between saidreciprocating member and said spindle, and means for a justablyanchoring an element of said differential mechanism for causingadvance-of said spindle, said m ans -,when adjusted being adapted tovary the lead and lag of said stroke through said dif- 1,429,308 I, v Q

advancement of said spindle through said. differential mechanism uponoperation of said reciprocating member, said manually adjustable devicebein adapted to vary the lead and lag of s'aic strokes whereby tomaintain a predetermined relation between said cutter and tool.

In testimony whereof I affix my signature in presence of two witnesses.

FRANZ' LOUIS WAGHTLER.

Witnesses:

RICHARD Trrnn'rn, GUSTAV MI'iLLER.

